It is known that automatic punch presses with transverse transport tongs must include special safety systems which switch off the main drive of the press as soon as an unforeseen obstacle comes into the operating zone of the tongs. Such an obstacle occurs, for example, when a workpiece is incompletely ejected from the die after the shaping operation. Thus, the workpiece can not be seized by the tongs. Consequently, the tongs come up against two workpieces in the subsequent transport phase. Further interruptions of operation of this sort are known to people skilled in the art and need not be discussed here.
The pairs of conveyor tongs are attached to the front end sections of carrying elements which carry out a periodical, to-and-fro sliding movement and must therefore always be lubricated. Flexible tubes are used to lubricate these parts which move to-and-fro at a high frequency. These flexible tubes, used in the prior art are subjected to strong wear due to the continually alternating stresses. Furthermore, these tubes are difficult to arrange in the very small space available.
Most importantly, two completely separate devices had to be used, one for the safety of the machine and another for lubrication of the tong jaw carriers. Such an arrangement is unfavorable because of the space requirements, the lack of structural simplicity and costs of the prior art system.